Optically Transparent Percolating Colloids Heated by Electronic Light Scattering

ABSTRACT Photothermal therapy of oncological diseases, based on the targeted delivery of light‐harvesting agents such as dyes, nanoshells, and photosensitizers, remains a major focus of the scientific community. However, light can be effectively captured by optically transparent media through a scattering mechanism rather than absorption. This is achieved in spatially confined media, e.g., foams, colloids, gels, and tumors, which can impart extra momentum to electrons under light illumination, thereby enhancing the optical oscillator strength through indirect optical transitions. Spatial confinement induces additional electronic states, boosting the cross section of electronic light scattering (ELS), a phenomenon that manifests as a featureless broadband background in Raman spectra. This work studies thermo‐optical behaviors of percolating colloidal systems using ELS. We theoretically and experimentally demonstrate that a water‐in‐decane system stabilized by sodium bis(2‐ethylhexyl) sulfosuccinate () under continuous‐wave laser illumination with the moderate intensity of 1 kW/cm 2 can be heated by several tens of degrees at the percolation point. This effect is shown to originate from energy band bending in the optically transparent system. These findings hold unprecedented promise for the development of targeted thermo‐optical detection and treatment of specific cancers.